Power semiconductor modules, or power modules, are used for various electrical power conversion applications. Example conversion applications may include, inversion applications for converting direct current (DC) power to alternating current (AC) power, rectification applications for converting AC to DC power, voltage conversion applications for converting DC power from one voltage to another, and frequency conversion applications for converting AC power from one oscillation frequency to another. One common operation that may be used in any of the foregoing power conversions may involve a controlled switching of one or more power switching devices between a conductive and a non-conductive state.
As the power switching devices in the module may be operated at relatively fast switching speeds, inductance due to the configuration of the circuit (“parasitic inductance”) can lead to increased power losses resulting from greater voltage and current oscillation and reduced reliability due to greater overvoltage stresses endured by the power switches.
To reduce the detrimental effects associated with the switching action of the module, relatively large capacitors may be externally located across the positive and negative DC buses or from each DC bus to an electrical return. These capacitors are commonly referred to in the art as “X” (across the power bus) or “Y” capacitors (from a given power bus to the electrical return). By “externally” it is meant that the elements referred to are located outside the power module. Unfortunately, the relatively long length of the electrical leads for connecting such external connectors and inductance associated with these leads make this approach somewhat ineffective.
In view of the foregoing considerations, it would be desirable to provide further improvements to power modules.